BOSTON — The World Series champion Boston Red Sox have exercised their $13 million option on left-hander Jon Lester.

Lester was the starting and winning pitcher twice during Boston’s six-game victory over the St. Louis Cardinals. The 29-year-old was 15-8 with a 3.75 ERA in the regular season. He went 4-1 with a 1.65 ERA in the postseason, including victories in Games 1 and 5 of the Series.

He had a 0.59 ERA in his two starts against St. Louis — the best by a Red Sox pitcher making more than one start in a World Series since Hugh Bedient in 1912.

In his career, Lester is 100-56 record with a 3.76 ERA in 221 regular season appearances. His 1,237 strikeouts are the most by a Red Sox left-hander.